Airline's attempt to save money by reducing the amount of fuel left when a plane lands undercuts their decision-making authority, pilots say. American says its strategy would leave ample reserves.

Aeronautics professor Les Westbrooks said the situation at American is troubling because it signals a further chipping away of the captain's authority, while the captain's responsibility for the safety of everyone on board hasn't changed.

"Everybody wants to tell the captain what to do, but if something goes wrong, it will be the captain who will lose his or her license," said Westbrooks, a retired Air Force and airline pilot who is an associate professor of aeronautical science at Embry-Riddle Aeronautical University in Daytona Beach, Fla.

He disagreed with American's assessment regarding reserve fuel. "Reserve fuel should not be touched," he said. "It is there for reserve."

Westbrooks said passengers should not be overly concerned about the fuel crunch issue, although there are potential safety ramifications that can go undetected until a problem arises, he said.

He cited two recent cases involving pilots flying for regional airlines — American Eagle Airlines and Trans States Airlines — who taxied their planes from the gate to runways with only one engine activated — a common fuel-conservation initiative practiced by most airlines. But the commuter pilots, who typically had less flight experience than their counterparts at major airlines, forgot to start the second engine before takeoff. The pilots aborted the takeoffs when cockpit warning systems notified them of a problem, and the planes exited the runways without flying, according to FAA investigations.

Since a fuel-price spike in 2008 threatened the industry with financial collapse, most major U.S. airlines have tried to better manage their fuel costs. American, United Airlines and US Airways have all culled flight data to better calibrate the amount of fuel loaded onto a plane to what historically has been consumed on the route based on traffic and weather conditions. The airline assessments take into consideration the different types of engines used on the same-model aircraft.

The amounts in dispute tend to be small: about 15 minutes of added reserves that pilots say they need to deal with heavy traffic, turbulence or other factors, sources said. But trimming even small amounts of fuel from every flight can produce substantial savings.

"This is a very sensitive issue, especially as fuel prices escalate," said aviation consultant Robert Mann.

American saved 111 million gallons of fuel in 2009 based on its Fuel Smart environmental program, which ranges from initiatives to shut off one engine while taxiing to stocking planes with lighter-weight beverage carts. American planes use about 2.7 billion gallons of fuel each year, Wagner said.

American has diverted flights to airports that were not the scheduled destination at a far higher rate than its network airline peers over the last two years, according to Bureau of Transportation Statistics data. In April, 0.32% of American flights were diverted, compared with 0.19% diverted at Delta Air Lines, 0.17% at Southwest Airlines and 0.14% at United.

"Does it raise the level of concern for the safety of the flight? It sure does," said John Plowman, president of Transport Workers Union Local 542, which represents American's flight dispatchers. With diversions, "the complexity of operations goes through the roof."